allowed string operators as variables names in assignments

CHANGELOG

@@ -1,6 +1,6 @@
 * 1.42.1 (2019-XX-XX)
 
- * n/a
+ * allowed string operators as variables names in assignments
 
 * 1.42.0 (2019-05-31)
 

src/ExpressionParser.php

@@ -649,7 +649,13 @@ public function parseAssignmentExpression()
         $stream = $this->parser->getStream();
         $targets = [];
         while (true) {
-            $token = $stream->expect(Token::NAME_TYPE, null, 'Only variables can be assigned to');
+            $token = $this->parser->getCurrentToken();
+            if ($stream->test(Token::OPERATOR_TYPE) && preg_match(Lexer::REGEX_NAME, $token->getValue())) {
+                // in this context, string operators are variable names
+                $this->parser->getStream()->next();
+            } else {
+                $stream->expect(Token::NAME_TYPE, null, 'Only variables can be assigned to');
+            }
             $value = $token->getValue();
             if (\in_array(strtolower($value), ['true', 'false', 'none', 'null'])) {
                 throw new SyntaxError(sprintf('You cannot assign a value to "%s".', $value), $token->getLine(), $stream->getSourceContext());

test/Twig/Tests/Fixtures/expressions/string_operator_as_var_assignment.test

@@ -0,0 +1,18 @@
+--TEST--
+Twig supports the string operators as variable names in assignments
+--TEMPLATE--
+{% for matches in [1, 2] %}
+    {{- matches }}
+{% endfor %}
+
+{% set matches = [1, 2] %}
+
+OK
+--DATA--
+return []
+--EXPECT--
+1
+2
+
+
+OK